Ciphertext policy attribute based encryption with immediate attribute revocation for fine-grained access control in cloud storage

With the advent of cloud computing, more and more organizations plan to adopt the cloud storage service allowing a data owner to outsource her data to the cloud service provider where the users are provided to access to the outsourced data. However, when the outsourced data are sensitive, the security and privacy of data have to be protected to eliminate the data owner´s concerns. Since in cloud storage systems, the data owner and the cloud server are not with the same trust domain, the honest and curious cloud server cannot be relied on to define and enforce the access control policy. To tackle this open problem, existing methods use the cryptographic techniques such as symmetric encryption or traditional public encryption scheme requiring the data owner to encrypt the data and distribute decryption keys to the authorized users, which incur the complicated key distribution and management. In this work, ciphertext policy attribute based encryption scheme is presented to achieve fine-grained access control. Furthermore, in the presented scheme, an immediate attribute revocation method is presented to handle the dynamic updates of users´ access privileges in cloud storage systems. Security analysis and performance evaluation show the proposed scheme is secure and efficient in cloud storage systems.